In asynchronous bidirectional communication links, the local transceiver has its own local reference clock and the remote transceiver has its own remote reference clock. The local reference clock may be used by both the transmitter circuitry of the local transceiver and the receiver circuitry of the local transceiver. As the local reference clock and the remote reference clock each have their own crystal, the local reference clock and the remote reference clock run at different rates due to the differences in the two crystals. These differences may be exacerbated by crystal aging. If the two crystals drift apart from each other, the difference in frequency between the local reference clock and the remote reference clock (i.e., frequency error) will increase the bit errors (and thus the bit error ratio (BER)) on the received link. This frequency error impairment is in addition to the transmission line loss, dispersion, crosstalk, and other physical impairments that are present in communication links with high data rates and long electrical distances.